13.1 Libraries

A Dylan library defines a software component — a separately compilable unit that can be either a stand-alone program or a component (library) of some larger program. The elements of the core Dylan language are in a library called dylan. The simplest Dylan program consists of at least two libraries: the original program source in the program library, and the dylan library, which supplies the predefined Dylan language elements used by the program library. A simple Dylan component may consist of only a single library — the component library. The component library will be used by other libraries. The component library will use definitions from the dylan library (and possibly other components). Hence, when combined with other components into a complete program, the program will consist of several libraries.

In each Dylan implementation, a library is associated with implementation-specific export information that is automatically maintained by the compiler. The library export information completely describes whatever implementation-specific information is needed for other software components to use the library. Thus, you can use libraries to deliver components in compiled form, keeping the implementation of the library confidential.

Comparison with C++ and Modula: Dylan libraries are similar to C++ libraries in that they both are potentially shared components of many programs. Unlike C++ libraries, Dylan libraries include all the information needed to be used by another Dylan library — there is no companion header file that must be kept up to date. Dylan libraries are analogous to Modula packages — all the information necessary to use a library is contained in the library.